Dissociations between face identity and face expression processing in developmental prosopagnosia

Individuals with developmental prosopagnosia (DPs) experience severe and lifelong deficits recognising faces, but whether their deficits are selective to the processing of face identity or extend to the processing of face expression remains unclear. Clarifying this issue is important for understanding DP impairments and advancing theories of face processing. We compared identity and expression processing in a large sample of DPs (N = 124) using three different matching tasks that each assessed identity and expression processing with identical experimental formats. We ran each task in upright and inverted orientations and we measured inversion effects to assess the integrity of upright-specific face processes. We report three main results. First, DPs showed large deficits at discriminating identity but only subtle deficits at discriminating expression. Second, DPs showed a reduced inversion effect for identity but a normal inversion effect for expression. Third, DPs' performance on the expression tasks were linked to autism traits, but their performance on the identity tasks were not. These results constitute several dissociations between identity and expression processing in DP, and they are consistent with the view that the core impairment in DP is highly selective to identity.